backfire

[baldyshinehead]

ok guys, before i go pocking about and messing things up thought i would ask.

gsx750, runs lovelly untill you get upto around 5000 revs, then sounds like its starvin, get to 6000 and it picks up again but stall's once the revs drop, also backfires :confused:

[dracken1]

are you running standard carbs /airfilters/exhaust system??? is it backfiring through the exhaust or the carbs:)

[baldyshinehead]

standard carbs, and exhaust, the air filter is standard but has been modified a little so the seat fits ( maybe its too much air ??? ) , backfiring through exhaust :(

[Borg]

sounds like there could be an air leak in the pipes, check the exhausts for holes or gaps, is it like an over run backfire ?

[baldyshinehead]

sounds like there could be an air leak in the pipes, check the exhausts for holes or gaps, is it like an over run backfire ?

the pipes are sound, welded all the holes up :rolleyes: it backfires when you let the throttle off after high revs only

[Dougie]

Running rich at high revs,unburnt fuel igniting in the pipe?

[baldyshinehead]

possibly ? i know i need to balance the carbs, could that cause it ?

[Borg]

Yep one could be pumping petrol in and it's just getting sucked through.

[baldyshinehead]

thanks one and all :D
gives me a couple of places to start lookin

[johnr]

also the early gsx motors(with the rectangular end caps on the ends of the cam cover) have a mechanical ignition advance mechanism which can rust nd seiz up either fully advanced or fully retarded. its under the r/h side engin cover. you might also check that the fuel filter in the tank isnt blocked, and the vacuum pipe to the fuel tap isnt perished.

[baldyshinehead]

thanks john :D